This invention relates to a method of uncovering and draining the preparation limit line of teeth in conjunction with the taking of impressions, cementing and conservative caries therapy by the aid of a retraction cord. The invention also provides a new and improved retraction cord for this purpose.
When taking an impression, for example, after preparation of a tooth for a crown or a bridge, it is necessary in almost every case to uncover the preparation limit line to obtain an optimal fit of the tooth substitute. To obtain such a fit, cords are currently used, which are soaked in diverse astringent solutions, such as adrenalin, aluminum chloride etc. Such a cord is pressed down into the gingival crevice between the tooth and the gum tissue and will uncover by its pressure the preparation limit line of the tooth. Due to the fact that the cord is soaked in an astringent, solution any bleeding will be checked. The drawbacks associated with the retraction cords currently used are several. To be capable, at all, of being pressed down between the tooth and the gum tissue, it must not be too thick, which will restrict the uncovering of the preparation limit line. The cord is saturated with an astringent solution. By reason of the risk of general side effects, not more than 7 centimeters of adrenalin-soaked cord should be used in every instance, which might prove necessary, however, in larger dental reconstruction works. Many cords in current use untwist when pressed down into the gingival crevice, which will render the application difficult; this is tedious and irritating and will risk the impression quality.